Capacitive acceleration sensors with a detection direction perpendicular to the wafer plane, referred to as z-sensors, often utilize balancing-rocker constructions. The sensor principle of these balancing rockers is based on a spring-mass system in which a movable seismic mass forms a plate-type capacitor together with two counter electrodes disposed on the substrate. The seismic mass is connected to the base via a torsion spring. If the mass structures on the two sides of the torsion spring are of different size, then an acceleration action will induce the mass structure to rotate relative to the torsion spring as axis of rotation. Such a mass difference is caused by, for example, an additional mass affixed asymmetrically to the torsion spring. The distance of the electrodes on the side having the larger mass therefore becomes smaller and greater on the other side. The resulting change in capacitance is a measure for the acting acceleration. The sensor principle of these balancing rockers is described in the EP 0 244 581 or EP 0 773 443.
A central element of this sensor type is its torsion spring. The torsion spring is determinative of the mechanical sensitivity of the sensor. Variations in the production process result in fluctuations in the width of the torsion springs, which greatly influence the sensitivity. In conventional balancing-rocker structures, these fluctuations in sensitivity are not compensated.